Contact lenses are a widely used and effective method for correcting vision, providing a comfortable alternative to eyeglasses for millions globally. These medical devices are considered safe for daily use when handled according to professional guidelines. The concern about whether contacts inherently damage the eye is unfounded; the lenses themselves do not cause harm. However, the risk of serious eye damage arises almost entirely from improper handling, cleaning, and wearing practices. Misuse creates an environment where the delicate tissues of the eye become vulnerable to injury and infection.
How Improper Use Leads to Eye Injury
The primary pathway for eye injury begins when a wearer ignores the prescribed schedule for lens wear. Overwearing contact lenses beyond the recommended daily duration restricts the flow of oxygen to the cornea, the clear front surface of the eye, which stresses the tissue. Sleeping in contact lenses significantly increases the risk of complications because the closed eyelid further reduces oxygen access and traps pathogens against the eye’s surface. This combination compromises the cornea’s natural defenses.
Substituting professional contact lens solution with improper liquids is another common error. Using tap water, distilled water, or saliva to rinse or store lenses introduces contaminants directly to the eye. Tap water can harbor microorganisms, including the dangerous Acanthamoeba, which causes severe, difficult-to-treat eye infections. Saline solution is not a disinfectant and fails to kill the bacteria and fungi that accumulate on the lens surface.
Poor hygiene practices related to the storage case also introduce pathogens. Failing to clean the case daily and allowing it to air dry, or neglecting to replace the case frequently, allows a biofilm of microorganisms to develop. Furthermore, “topping off” the old solution in the case with fresh solution dilutes the disinfecting agents and allows bacteria to thrive. These lapses in routine care disrupt the eye’s protective barriers.
Medical Conditions Associated with Lens Misuse
When contact lens misuse compromises the cornea, a range of specific medical conditions can develop that can affect vision permanently. One significant consequence of overwearing is corneal hypoxia, a state of oxygen deprivation. The cornea is naturally avascular, relying on direct absorption of oxygen from the air through the tear film.
In response to chronic oxygen depletion, the eye attempts to compensate by growing new blood vessels into the cornea, known as neovascularization. These abnormal vessels compromise the transparency of the corneal tissue. If they grow far enough, they can permanently obscure vision. This process is a visible sign of long-term tissue stress caused by inadequate oxygen supply, often resulting from wearing lenses for too many hours a day.
A sight-threatening result of poor hygiene and water exposure is microbial keratitis, a severe infection of the cornea. This condition, caused by bacteria, fungi, or the Acanthamoeba parasite, leads to an open sore or corneal ulcer. Overnight wear is the single most common risk factor for this infection. If left untreated, the resulting scarring can cause permanent vision loss or require a corneal transplant.
Physical irritation or a poor lens fit can cause a corneal abrasion, which is a scratch on the cornea’s outer layer. Abrasions occur when a foreign particle, like dust or debris, becomes trapped between the lens and the eye, or if the lens has a chipped edge. These small injuries create an entry point for infectious agents, potentially progressing to a corneal ulcer.
An allergic or inflammatory reaction known as Giant Papillary Conjunctivitis (GPC) can develop over time. GPC involves the formation of large, dome-shaped bumps, or papillae, on the inner surface of the upper eyelid. This condition is often triggered by protein deposits that accumulate on the lens surface or friction from the lens rubbing against the eyelid. Symptoms include itching, excessive mucus production, and the feeling that the lens is moving on the eye, often requiring a temporary cessation of lens wear.
Non-Negotiable Rules for Contact Lens Safety
Adherence to strict hygiene and wearing protocols is the most effective way to mitigate the risks associated with contact lens wear. Before touching a contact lens, hands must be thoroughly washed with soap and water, then completely dried with a clean towel. This simple step prevents the transfer of pathogens or water contaminants to the eye.
The replacement schedule prescribed by an eye care professional must be followed precisely. Daily disposable lenses should never be reused, and two-week or monthly lenses must be discarded after their designated lifespan. Extending the use of a lens allows proteins and debris to build up on the surface, increasing the likelihood of both infection and allergic reactions like GPC.
Only fresh, manufacturer-recommended disinfecting solution should be used for cleaning and storage. It is crucial to never mix old solution with new solution or use water for any part of the cleaning process. After lenses are stored, the case should be emptied, rinsed with new solution, and left open to air-dry, and the case itself must be replaced at least every three months.
Finally, contact lenses should never be worn while sleeping or when exposed to water, such as in the shower, pool, or hot tub, due to the greatly increased risk of severe infection. Regular, annual checkups with an eye care provider are necessary to ensure the lenses continue to fit correctly and to monitor the health of the cornea for any early signs of hypoxia or irritation.